The semiconductor industry's drive for higher device densities, better device performance, and lower cost has led to the development of integrated circuit transistors that are three-dimensional in the sense of making greater use of space perpendicular to the substrate surface. One such transistor is the FinFET. A FinFET is a field effect transistor (FET) having a channel formed in a fin-like structure of semiconductor extending from a substrate surface. This geometry allows one or more gates to wrap around the channel and/or act on the channel from its sides. This improves control over the channel and reduces short channel effects in comparison to a more conventional structure in which a single plane separates the channel from its gate. The fin-like structure also allows the channel to be extended vertically, increasing its cross-sectional area and permitting a higher current without increasing the transistor's footprint.
Further improvements include replacing the usual silicon channel material with a high mobility semiconductor. High mobility semicońductors generally have a smaller bandgap and higher dielectric constant than silicon. Candidate materials include compound semiconductors, e.g., compounds of Group III and Group V semiconductors. Electrostatic control is reduced when high mobility semiconductors are used. Implant doping to create isolation wells is also more difficult when high mobility semiconductors are used.